RT Journal Article SR Electronic T1 E-cigs have lower levels of harmful toxins JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP E331 OP E331 DO 10.1503/cmaj.1095396 VO 189 IS 8 A1 Roger Collier YR 2017 UL http://www.cmaj.ca/content/189/8/E331.abstract